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[Bug 1560552] Comment bridged from LTC Bugzilla


------- Comment From hbathini@xxxxxxxxxx 2016-04-28 09:20 EDT-------
Mahesh spoke to PPC Maintainer offline about this patch. Since the changes are more invasive (and at the code path which is used at every boot) review is taking time. Maintainer is also thinking about alternate solution but that includes rewriting lots of cpu numbering code. So as of now maintainer conveyed that he needs some more time (hasn't mention specific time) to review this patch to be very sure that it is not harmful.

So as it stands, this patch may not be going anywhere at least for some


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  ISST-LTE: pVM:high cpus number need a high crashkernel value in kdump

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  Fix Released

Bug description:
  The kdump kernel will be booted with "maxcpus=1", so no matter how many cpus this system has, only one cpu will be brought up during kdump I think. But on LPAR thymelp2, if we allocate 40 cpus on it, then kdump works just fine with 512M  as crashkernel value. But if we allocate 200 cpus on it, kdump fails by trggering OOM. It has been proved that in latter situation we need 1.5G RAM reserved for kdump to let it works.
  Contact Information = Ping Tian Han/pthan@xxxxxxxxxx Carrie Mitsuyoshi/carriemi@xxxxxxxxxx 
  ---uname output---
  Linux thymelp2 4.2.0-23-generic #28~14.04.1-Ubuntu SMP Thu Dec 31 13:41:19 UTC 2015 ppc64le ppc64le ppc64le GNU/Linux
  Machine Type = 8247-22L, LPAR 
  A debugger was configured, however the system did not enter into the debugger
  ---Steps to Reproduce---
   1. configure kdump with crashkernel=512M on thymelp2
  2. allcoate 40 cpus on thymelp2 and trigger kdump
  3. allocate 200 cpus on thymelp2 then do kdump again
  *Additional Instructions for Ping Tian Han/pthan@xxxxxxxxxx Carrie Mitsuyoshi/carriemi@xxxxxxxxxx: 
  -Post a private note with access information to the machine that the bug is occuring on.

  == Comment: #1 - Nadia N. Fry <nadiaf@xxxxxxxxxx> - 2016-02-19 13:53:02 ==
  Any update?

  == Comment: #2 - Hari Krishna Bathini <hbathini@xxxxxxxxxx> - 2016-02-22 03:40:05 ==
  Mahesh posted a patch upstream which should take care of this problem



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